Refrigeration system with closed circuit circulation

ABSTRACT

A refrigeration system having a closed circulating circuit filled with a refrigerant which on evaporation expands and gives rise to an increase in pressure in the whole or in parts of the circulating circuit, and which at ambient temperature has a saturation pressure that is higher than the maximum working pressure in the refrigeration circuit. A refrigeration of this kind may, for example, be carbon dioxide. By allowing vaporized refrigerant to condense against the surface of the refrigerant in liquid phase, contained in a container that is insulated and has adapted size and adapted liquid level, the pressure in the circulating circuit can be maintained below the maximum working pressure of the refrigeration circuit. Thus undesirable build-up of pressure in the event of, e.g., a period of inoperation or breakdown, is prevented, and the circulating circuit of the refrigeration system can be designed and made for a pressure which is below the saturation pressure at ambient temperature of the refrigerant used, and the refrigeration system can be made using conventional or at least virtually conventional elements, whereby the total system costs are reduced considerably in relation to a total system which is built to withstand higher pressure, e.g., the saturation pressure at room temperature of the refrigerant. Starting up after, e.g., a period of inoperation or breakdown is secured with valves which provide a controlled fall in pressure in an insulated container after an increase in pressure in the same container exceeding the maximum working pressure of the circuits.

The present invention relates to a refrigeration system having a closedcirculating circuit filled with a refrigerant intended for heattransfer, which refrigerant at atmospheric pressure has a saturationpressure that is higher than maximum working pressure in the circulatingcircuit, which refrigeration system consists at least of one or moreevaporators or heat exchangers, equipment for circulation of therefrigerant and one or more condensers, and also at least one containerfor the refrigerant in connection with the refrigeration circuit.

In recent years concern for the environment has brought about a changein the use of refrigerants in refrigeration systems/heat pumps for, e.g.refrigerated cabinets in grocery shops, air cooling. refrigeratedtransport and refrigerated storage rooms. This change is primarilyrelated to the fact that the vast majority of synthetic refrigerantswhich were used earlier (e.g., chlorofluorocarbons), if released, led toa depletion of the ozone layer in the stratosphere, and thus alsoincreased ultraviolet radiation. The use and thus the emissions of theserefrigerants have now been regulated through international agreements.and stringent national and international requirements mean that a greatmany synthetic refrigerants (CFC refrigerants) can no longer be used.

To compare the different refrigerants and their environmental impact, itis essential to examine their ozone depletion potential (ODP) andgreenhouse warming-up potential (GWP). An overview of refrigerants thathave conventionally been used in refrigeration systems in e.g., groceryshops, is as follows:

    ______________________________________                                                                         Greenhouse                                                                    warming-up                                                        Ozone depletion                                                                           potential (GWP)                                                   potential (ODP),                                                                          (100 years),                                 Refrigerants                                                                          Not available after:                                                                       (CFC11 = 1) (CO2 = 1)                                    ______________________________________                                        CFC - 12                                                                              1995         1           7100                                         CFC - 502                                                                             1995         0.32        4300                                         HCFC - 22                                                                             2014         0.055       1600                                         ______________________________________                                    

Halocarbons may be used to replace these refrigerants. These do notdestroy the ozone layer, but still contribute to the greenhouse effect.Examples of some such refrigerants are:

    __________________________________________________________________________                               Evap. Ozone Gr.house                                                  Based on                                                                              temp. depletion                                                                           warming-                                                  (% age) Temp. potential                                                                           up pot.                                Refrigerants:                                                                        Replace:                                                                            Producer                                                                            (other comm.)                                                                         fluct.                                                                              (ODP) (GWP)                                  __________________________________________________________________________    HP 62  CFC 502                                                                             DuPont                                                                              HFC134a 4%                                                                            -46.1° C.                                                                    0     2650                                   HCF 404A                                                                             HCFC 22     HFC125 44%                                                                            0.7                                                R-404A             HFC143a 52%                                                Klea 60                                                                              CFC 502                                                                             ICI   HFC32 20%                                                                             -42.2° C.                                                                    0     1575                                          HCFC 22     HFC125 40%                                                                            6.6                                                R-407B             HFC134a 40%                                                Klea 61                                                                              CFC 502                                                                             ICI   HFC32 10%                                                                             -45.1° C.                                                                    0     2290                                          HCFC 22     HFC125 70%                                                                            4.4                                                R-407B             HFC134a 20%                                                Genetron                                                                             CFC 502                                                                             Allied                                                                              HFC125 50%                                                                            -45.8° C.                                                                    0     2720                                   AZ-50  HCFC 22                                                                             Signal                                                                              HFC143a 50%                                                R-507              (Azeotrope)                                                HCF 134a                                                                             CFC12 All           -26.5° C.                                                                    0     1200                                   R-134A       producers                                                        __________________________________________________________________________

In addition, natural refrigerants such as, e.g., ammonia (NH₃), carbondioxide (CO₂) and propane (C₃ H₈) can be used. These refrigerants havevirtually no ozone depletion potential and, with the exception of carbondioxide, they have almost no greenhouse warming-up potential. However,the use of CO₂ as a refrigerant cannot be looked upon as a contributionto the greenhouse effect as reutilisation is assumed.

Of these naturally occurring refrigerants, ammonia and carbon dioxideare considered to be the most suitable and environmentally saferefrigerants that can be used. When using ammonia as a refrigerant,known technology is employed which is adapted to the individual use andsystem, but this medium is toxic and under certain circumstances it isflammable. This means that a brine should be used as a secondary agentfor the individual applications in the refrigeration circuit. The sameapplies when using propane as a refrigerant.

The use of carbon dioxide as a refrigerant is previously known, but whensynthetic refrigerants were introduced, the use of carbon dioxide forthis purpose was greatly reduced, a fact also attributable to a numberof drawbacks connected to carbon dioxide as a refrigerant.

These drawbacks include the fact that the temperature gap between thecritical temperature and the so-called triple point is relatively smallcompared with traditional refrigerants. This means that when CO₂ is usedin an ordinary refrigeration process, the carbon dioxide will for themost part be used in a temperature range of from -50° C. (evaporation)to about -5° C. (condensation) with a reasonable coefficient ofperformance. This means that carbon dioxide is rather inflexible withrespect to different applications (temperature levels). The individualsystem must therefore be adapted to the individual application.

A further drawback when using CO₂ as refrigerant compared withconventional refrigeration systems, is associated with the rise inpressure which occurs when the temperature of the refrigerant passesfrom working temperature to ambient temperature. At room temperature thesaturation pressure of carbon dioxide is about 50 to 60 bar, and this isconsiderably higher than the working pressure in a conventionalrefrigeration system. This means that in the event of a breakdown, thesaturation pressure will rise in the circulating circuit as thetemperature rises, and if the circuit is to be capable of (withstandingsaturation pressure at ambient temperature, the individual components inthe refrigeration circuit must be designed for this high pressure, whichmeans a sharp increase in costs compared with conventional refrigerationsystems.

In connection with this problem, it is previously known from. e.g., U.S.Pat. No. 5.042.262 that a refrigeration system using carbon dioxide asrefrigerant, when the system is not operating, will maintain a pressurein the refrigeration circuit of less than about 17 bar by either amechanical cooling of the refrigerant in the circulating circuit or by apressure relief means which releases the vaporised carbon dioxide intothe environment in order to adjust the pressure. In large systems, amechanical cooling of the whole of or parts of the refrigeration circuitto reduce the pressure when the system is not in operation will resultin a considerable rise in installation and maintenance costs. If therefrigerant is released through a pressure relief valve in order tomaintain the pressure in the refrigeration circuit below the maximumworking pressure, this will involve adding a new refrigerant whenstarting up the system, which involves costs, in addition to theindirect cost of the refrigeration system being inoperative pending arefill of refrigerant.

Furthermore, from U.S. Pat. No. 4,693,737 it is known to use carbondioxide as brine in a secondary circuit of a refrigeration system. Inthis case, the refrigerant in the secondary circuit is stored in a largetank in liquid form and the individual applications in the circuit arecooled by evaporation of liquid CO₂. The tank is kept cooled by theprimary circuit and on the return of vaporised CO₂ in the secondarycircuit it is condensed in the storage container. If the system is notin operation, the vaporised CO₂ will condense against the surface of thecontents in the container, but after some time the condensation willabate, with a subsequent increase in pressure which is limited byreleasing vaporised CO₂ from the secondary circuit.

Moreover, U.S. Pat. No. 4,986,086 makes known a refrigeration systemwhere a refrigerant, preferably carbon dioxide, is used, where therecommended maximum working pressure is about 35 bar. Evaporation whichresults in additional pressure is controlled by releasing CO₂, from thesystem into the environment. This ventilation takes place chiefly from acontainer in the system which can accommodate a higher pressure than theworking pressure in the rest of the refrigeration system.

Another two-stage cooling process using carbon dioxide in the secondarycircuit is described in GB 2 258 298 A. The secondary circuit in thissystem is described as having a maximum working pressure of about 34bar, which is said to be higher than normal in a refrigeration system ofthis kind. This calls for a special design of the various elements inthe refrigeration circuit in order to handle this high pressure. In theevent of a breakdown or a period of non-operation, it is not stated howan additional increase in pressure as a result of the effect oftemperature from the surroundings is dealt with.

To maintain the temperature, and thus the pressure, in a container ofcarbon dioxide at a relatively low level when, e.g., transporting carbondioxide, it is known from WO 88/04007 to insulate a container that is tohold carbon dioxide. In addition to insulation, it is known from WO93/23117 to provide a separate refrigeration unit in connection with acontainer that is to hold carbon dioxide with a view to maintaining thetemperature, and thus the pressure, at a favourable level in relation tothe maximum working temperature in the storage container.

The use of carbon dioxide in a single application in connection with arefrigeration unit, where carbon dioxide is contained in an insulatedtank, is also described in U.S. Pat. No. 4,129,432 and U.S. Pat. No.4,407,144. In these systems, carbon dioxide is released into theenvironment after evaporation.

In the Nordic Refrigeration Journal ("Kulde-Skandinavia") No. 5/96,there is a discussion on pages 25 to 28 of the disadvantages andadvantages which arise when using carbon dioxide as a refrigerant, andit is pointed out that carbon dioxide in refrigeration systems requiresthe system to have been built for especially high pressure, e.g., 120 to140 bar, and even for a low temperature operation with a design pressureof 25 to 40 bar, it is necessary to install supplementary equipment inorder to cope with an inoperative situation. Similar problems are alsopresented in the article on pages 34 to 37 and page 60 in the NordicRefrigeration Journal ("Kulde-Skandinavia"), No. 4/96. Special attentionis directed to the situation that arises when the system is not inoperation, where the saturation pressure in the refrigerant exceedsmaximum working pressure.

SE 9202969 describes a cooling system where a container in a circulatingcircuit is located between a first and a second pressure reducing means.The purpose of the is container is to collect coolant in order to passthis into the screw compressor between the inlet and outlet of thecompressor, in order to cool the screw compressor. Furthermore, a valveis installed which controls the flow of the gaseous coolant through theduct from the container to the screw compressor. A container is placedin the cooling circuit, but the pressure in parts of the cooling circuitis reduced further after the container by pressure reducing means and ifthe system stops operating, the coolant will be able to flow back to thecontainer as it assumes ambient temperature and the pressure eventuallyincreases, whereupon gaseous coolant will be able to condense againstthe surface of the liquid coolant in the container. However, this willnot take place immediately from the parts of the system where thepressure is lower. i.e., after the pressure reduction valve.Furthermore, there is no disclosure of specific distinctive features ofthe container or the location of the pressure regulating means inconnection therewith which enable the container to be a receptacle forvaporised coolant with the intention that this should to the greatestextent possible be condensed against the surface of the coolant in thecontainer to be subsequently a storage container for coolant in a systemthat is not in operation.

In DK 159894B, as in the aforementioned Swedish patent publication, acontainer is also located in a cooling circuit. The container is dividedinto two chambers and the purpose seems to be that a recirculationnumber greater than 1 is obtained, whereby the liquid and vapourcirculate together in the cooling circuit, which gives better heattransfer in the evaporator. A valve system is provided in connectionwith the container, which helps to maintain the liquid levels in theseparate chambers at the desired level, and also to contribute to apressure equalisation between the chambers. Nor in this patentpublication is the container designed for receiving coolant in vapourform in order that this should subsequently be condensed against thefree surface of the coolant, and the container is thus not provided withthe means which are necessary if the container is to have this function.

One of the objects of the invention is to overcome the drawbacks thatare associated with the prior art, and the refrigeration system ischaracterised according to the invention in that there is provided atleast one insulated tank for the refrigerant in connection with therefrigeration circuit, which container is sufficiently proportioned andinsulated and sufficiently filled with refrigerant in liquid phase sothat at least parts of the vaporised refrigerant in the refrigerationcircuit condense against the liquid surface in the container, and thatthe saturation pressure in the circuit essentially does not exceedmaximum working pressure of the whole of or parts of the refrigerationcircuit.

Additional embodiments of the refrigeration system are set forth in theattached patent claims and in the following description with referenceto appended drawings.

The present invention provides a solution which enables a refrigerationsystem to be built primarily of conventional elements which require amaximum working pressure that is below the saturation pressure of therefrigerant used at ambient temperature. This will be the case, forexample, when using carbon dioxide as refrigerant in most instances, ascarbon dioxide at normal room temperature has a saturation pressure inthe range of 50 to 60 bar which is higher than the normal maximumworking pressure for a refrigeration system consisting of conventionalelements. Furthermore, the present invention provides a solution wherevaporised refrigerant, which will result in an increase in pressure inthe refrigeration system, is not released through the pressure reliefvalve if the system is inoperative and affected by the temperature fromthe surroundings. This is to obviate the necessity of refilling therefrigeration system with refrigerant before it can be restarted. Anideal situation in this case would be that the refrigerant, in the eventof a breakdown, is practically completely received in the containerwithout the pressure exceeding maximum working pressure, so that therefrigeration system can be restarted without adding fresh refrigeranteven if during the breakdown the refrigerant has reached a temperaturethat is considerably closer to the ambient temperature of the systemthan the working temperature of the refrigerant. Furthermore, theconcept of the present invention will limit the build-up of pressure inthe event of a breakdown, so that if the system is restarted after arelatively short time, this will happen without the refrigerant beingreleased, or without the saturation pressure of the refrigerant havingexceeded the maximum working pressure in the system.

By arranging in the refrigeration circuit an insulated container whichis adapted as regards size, insulation and rate of admission of therefrigerant in liquid phase, it will be possible, in the event of abreakdown, to maintain the temperature in the container at a level suchthat vaporised refrigerant returning to the container will condenseagainst the surface of the liquid phase in the container and thus reducethe rise in pressure owing to evaporation in the circulating circuit. Bydesigning the container so that wall thickness, insulation, magnitude ofthe liquid surface and size of the tank in other respects help to keepthe temperature in the tank stable even in the event of a breakdown, itwill be possible to obtain considerably lower increase of pressure pertime unit in the circuit than by using an uninsulated container of thestandard type. Furthermore, it will be possible to construct thecontainer so that the whole of or parts of the quantity of fluid in thecirculating circuit condense in the container before the saturationpressure exceeds maximum working pressure in the circuit if the systemis not operating.

As a result, a refrigeration system, for example, for grocery shops, maybe produced using conventional elements for moderate working pressurewhich is considerably lower than the saturation pressure of therefrigerant at ambient temperature. In the event of a breakdown,according to the invention, it will be possible to condense vaporisedrefrigerant in the insulated container, thereby maintaining a pressurein the refrigeration system which does not exceed maximum workingpressure.

If, in addition, there are provided manual or automatic valves forclosing the connections in/out of the container with a bypass of thevalves, where there is provided a check valve, it will be possible toallow vaporised refrigerant to return to the insulated container andcondense, in order thus to maintain a pressure in the circulatingcircuit which is lower than maximum working pressure. Safety valves mayalso be provided which, in the event of an undesirable build-up ofpressure in the circulating circuit, release vaporised refrigerant intothe surroundings.

If the container is designed for a higher pressure, below, equal to orabove the saturation pressure of the refrigerant, all of or parts of therefrigerant can be stored in the container after condensation forvarying periods of time or indefinitely.

Starting up after, e.g., a period of inoperation or a breakdown, issecured by valves which give a controlled fall in pressure in theinsulated container after a rise in pressure in the same container abovethe maximum working pressure in the circuits.

The invention will now be described in more detail with reference toappended FIGS. 1 to 4 which illustrate different embodiments of theinventive concept.

FIG. 1 describes an ordinary refrigeration system according to theinvention where an insulated tank is used as a low pressure receiver.

FIG. 2 shows a system where the refrigerant circulates from a fluidcontainer according to the present invention by means of a pump orself-circulation.

FIG. 3 shows a system similar to that in FIG. 2, where the presentinvention is used in a secondary circuit.

FIG. 4 shows a system similar to that in FIG. 3, where the presentinvention is used in a secondary circuit, wherein anevaporator/condenser-device may be designed for lower pressure than thesaturation pressure of the refrigerant at ambient temperature.

FIG. 1 shows a refrigeration system having an insulated container 1 forthe refrigerant in liquid phase and gas phase, and a circuit with intake4 of the refrigerant in liquid phase, to evaporators 2 and then via areturn pipe 5 to an insulated tank 1. From the tank 1 vaporisedrefrigerant then passes to the compressor 6 and then to the condenser 3and then back via intake 7 to intake 4 via a heat exchanger in theinsulated tank 1. On each of the pipe connections where the refrigerantis in the vaporised state there is arranged a safety valve 20 which, inthe event of a build-up of pressure in the piping in excess of maximumworking pressure, releases vaporised refrigerant into the surroundings.According to the invention, vaporised refrigerant in the return pipe 5and the intake 8 will be capable of being conveyed back to the insulatedtank 1 and, when the refrigeration system is inoperative, the vaporisedrefrigerant will be able to condense therein against the surface of therefrigerant in liquid form in order thus to maintain the saturationpressure in the refrigerant below the maximum working pressure of therefrigeration circuit without releasing vaporised refrigerant throughthe pressure relief valves or safety valves 20 to 22. In the event of abreakdown in the system, the valves 13 can be closed manually orautomatically, and at bypass 14 there is arranged a check valve 15 whichallows vaporised refrigerant to enter the insulated container 1 as thepressure rises in those parts of the refrigeration circuit where thetemperature of the refrigerant rises as a result of the ambienttemperature around the refrigeration system.

The valves 40 and 41 allow for a controlled fall in pressure in theinsulated tank 1 after an increase in pressure in the same tank abovethe maximum working pressure in the circuits owing to, e.g., a period ofinoperation or a breakdown. The controlled fall in pressure is due tothe operation of the refrigeration system or direct condensation in thecondenser. During the fall in pressure it is important that the tank 50,condenser or associated pipe section have the necessary volume toaccumulate condensed liquid during the fall in pressure. Moreover,evaporators 2 which, for example, may be freezer cabinets in a groceryshop or the like, are provided with valves etc. as in a normalconventional refrigeration circuit.

FIG. 2 shows a refrigeration system essentially like that in FIG. 1 butwhere the intake 7 from the condenser 3 to the insulated tank 1 does notpass in a closed circuit with the intake 4 from the insulated tank 1 toevaporators 2. In this case, there is also provided on the intake 4 anautomatic or manual valve 13 which can be closed if the refrigerationsystem breaks down. Moreover, a pump 9 may be provided for liquidtransport of the refrigerant; alternatively the system may be based onself-circulation. This refrigeration system is also made in accordancewith the inventive concept in that the container 1 is insulated andadapted in size and admission rate so that if the system breaks down,the refrigerant in the refrigeration circuit will be affected by theambient temperature, whereby an increase in pressure will take place andvaporised refrigerant will be able to return to the insulated tank 1 viathe pipes 5 and 8. As the insulated tank 1 is made according to theinvention, the vaporised refrigerant will condense in the tank againstthe surface of the refrigerant in liquid phase and pressure increase inthe refrigeration system will be moderated.

In FIG. 3 the present invention is used in a part of a secondaryrefrigeration circuit. In this case, the refrigeration circuit works inconnection with a refrigeration system 30 through anevaporator/condenser device 31, 3 where the outflow 8 from the insulatedtank 1 circulates through the condenser 3 and returns via the intake 7to the insulated tank 1. The circuit with evaporators 2 is in otherrespects the same as that in FIGS. 1 and 2, and in this system too itwill be possible, in the event of a breakdown, for vaporised refrigerantto return to the insulated tank 1, whereby according to the invention itcondenses against the surface of the refrigerant in liquid phase and thebuild-up of pressure in the refrigeration system is retardedconsiderably.

In FIG. 4 the present invention is used in a part of a secondaryrefrigeration circuit as in FIG. 3. In this case, the refrigerationcircuit works in connection with a refrigeration system 30 through anevaporator/condenser device 31, 3 where the outflow 8 from the insulatedtank 1 circulates through the condenser 3 and returns via the intake 7to the insulated tank 1. The valves between 3 and 7, 8 mean that thecondenser device 3 can be designed for a lower pressure than theinsulated tank 1. The circuit with evaporators 2 is in other respectsthe same as that in FIGS. 1, 2 and 3, and in this system too it will bepossible, in the event of a breakdown, for vaporised refrigerant toreturn to the insulated tank 1, whereby according to the invention itcondenses against the surface of the refrigerant in liquid phase and thebuild-up of pressure in the refrigeration system is retardedconsiderably.

The container 1 will thus form a part of the circulating circuit as alow pressure receiver, optionally as a liquid container where therefrigerant is used as a secondary agent.

By also designing the container 1 for a higher pressure and by providingit with the valves 13, 14 and 15 and also the valves 20, 21 and 22adapted to the dimensioning of respectively the circulation system,container and optionally compressor/condenser, parts of or all of therefrigerant supply can be stored for varying lengths of time orindefinitely.

When the refrigerant evaporates in the applications 2 and latercondenses against the cold liquid surface in the tank 1, the relationbetween the condensation heat and the specific heat of the liquid willbe crucial, and by insulating the tank 1 adequately and also ensuringthere is a sufficient liquid volume, it will be possible to obtain anincrease in pressure in the refrigeration system, for example, in therange of 2 bar per hour or less. Alternatively, all of or parts of thequantity of fluid in the circulating circuit will condense in thecontainer or plurality of containers 1 before the saturation pressure inthe refrigeration circuit exceeds maximum working pressure, even whenthe refrigeration circuit has reached approximately ambient temperature.If the breakdown is prolonged, the temperature in the insulatedcontainer 1 will rise so that the pressure here exceeds the maximumworking pressure in the refrigeration circuit, but because of the valves13 and the check valves 15, this rise in pressure will not spread to therest of the refrigeration system, and if the pressure exceeds themaximum working pressure of the insulated tank, a pressure relief orsafety valve 21 in association with the tank, located as shown on theoutlet 8 from the tank 1 in FIGS. 1-4, will be able to release vaporisedrefrigerant and thus control the pressure in the container 1. Thisinvolves loss of refrigerant and when starting the refrigeration systemafter a breakdown, this loss must be replaced by adding freshrefrigerant. However, this situation can be greatly retarded oreliminated by using the present invention, and moreover refrigerationsystems for the type of refrigerant discussed in connection with thepresent application, for example, carbon dioxide, can be designed andconstructed for a considerably lower working pressure than thesaturation pressure of the vaporised refrigerant at the ambienttemperature of the refrigeration system. This reduces the costs of therefrigeration system considerably in that purpose-built elements arelargely avoided and in that valves, pipes etc. will only take up asubstantially lower load than would be the case if the system were to bedesigned for the saturation pressure of the refrigerant at ambienttemperature.

What is claimed is:
 1. A refrigeration system having a closedcirculating circuit filled with a refrigerant intended for heattransfer, which refrigerant at ambient temperature has a saturationpressure that is higher than the maximum working pressure in thecirculating circuit, which refrigeration system consists at least of oneor more evaporators or heat exchangers, equipment for the circulation ofthe refrigerant and one or more condensers, and also at least onecontainer for the refrigerant in connection with the refrigerationcircuit, characterised in that the container (1) is insulated and isdesigned for a pressure, less than, equal to or higher than thesaturation pressure of the refrigerant at ambient temperature, whichcontainer (1) is sufficiently filled with refrigerant in liquid phasefor at least parts of the vaporised refrigerant in the refrigerationcircuit to condense against the liquid surface in the container (1), andthat in association with the container there is provided at least onepressure relief valve (21) which releases refrigerant when thesaturation pressure exceeds the maximum working pressure of the tank. 2.A refrigeration system having a closed circulating circuit according toclaim 1, characterised in that the refrigerant is carbon dioxide (CO₂).3. A refrigeration system having a closed circulating circuit accordingto claim 1, characterised in that in association with the circulatingcircuit there is provided at least one pressure relief valve (20) whichreleases refrigerant when the saturation pressure exceeds the maximumworking pressure of the circulating circuit.
 4. A refrigeration systemhaving a closed circulating circuit according to claim 1, characterisedin that the connections between the insulated container (1) and thecircuits to the peripheral components in the circulating circuit areprovided with manual or automatic valves (13) designed to close beforethe saturation pressure exceeds the maximum working pressure in thewhole of or parts of the circuits.
 5. A refrigeration system having aclosed circulating circuit according to claim 4, characterised in thatthere are provided check valves (15) in connection with the manual orautomatic valves, which check valves (15) allow vaporised refrigerantonly to enter the insulated container from the other components in thecircuits.
 6. A refrigeration system having a closed circulating circuitaccording to claim 1, characterised in that the insulated container (1)forms a part of a circulating circuit as a low pressure container.
 7. Arefrigeration system having a closed circulating circuit according toclaim 1, characterised in that the insulated container (1) forms a partof the circulating circuit as a fluid container where the refrigerant isused as a secondary medium.
 8. A refrigeration system having a closedcirculating circuit according to claim 1, characterised in that there isprovided a valve (40), which valve (40) allows vaporised refrigerant toenter the compressor (6) from the insulated container (1) at controlledpressure after the valve (40) in order to obtain a controlled fall inpressure in the insulated container (1) after an increase in pressure inthe same insulated container (1) above the maximum working pressure inthe circuits.
 9. A refrigeration system having a closed circulatingcircuit according to claim 1, characterised in that there is provided avalve (41), which valve (41) allows vaporised refrigerant to enter thecondenser (3) from the insulated container (1) at controlled pressureafter the valves (41) and via condensation in the condenser (3) toobtain a controlled fall in pressure in the insulated container (1)after an increase in pressure in the same insulated container (1) abovethe maximum working pressure in the circuits.
 10. A refrigeration systemhaving a closed circulating circuit according to claim 1, characterisedin that there is necessary volume in the container (50) or in thecondenser (3) or in the pipe section between condenser (3) and pipesection (7) to accumulate condensed refrigerant during a controlled fallin pressure in the insulated tank (1) after an increase in pressure inthe same insulated container (1) above the maximum working pressure inthe circuits.